Thesis subject

Impacts of foliar nutrient status on forest carbon sequestration in response to nitrogen and phosphorous additions

The Environmental Systems Analysis Group provides the possibility for students to do their thesis in collaboration with our group. This is one of many possible thesis subjects. Please feel free to contact professor De Vries (right) for more information.

Biomass production of forests and the related carbon sequestration is influenced by various drivers affecting net photosynthesis, including (i) climate change (i.e. temperature and precipitation), (ii) air quality change  (availability of carbon dioxide (CO2) and exposure to “toxic” elements, including ozone (O3) and sulphur dioxide (SO2) and (iii) the availability of nutrients, specifically nitrogen (N) and phosphorus (P) but also potassium, calcium and magnesium (K, Ca, Mg). There are many indications that forest production is largely influenced by nutrient availability and this also holds for the impacts of changes in climate and air quality on forest production. As N and P are most often the limiting factors for plant growth, this research focuses on those two elements. Assuming that the ratio of N and P in plant tissue gives an indication of the relative availability of these nutrients in the soil, we hypothesize that tree species have a 'critical' N:P ratio in foliage that tells us whether growth of the tree species is N-limited or P limited or co-limited.

One aim of a thesis or internship in this context is to (further) assess the impact of N and P addition on growth and carbon sequestration and assess the C/N or C/P performance versus the foliar N/P ratio (and the foliar N and  P contents). This will be done by combining (an ongoing) meta-analysis on nutrient enrichment experiments assessing single-nutrient effects (N and P vs. control) vs. combined nutrient effects (NP vs. control) with foliar N and P contents and foliar N:P ratios in leaves or needles of the trees of unfertilized control plots. Another aim includes an assessment in regional variation in N and P limitation and co-limitation in relation to site properties, climate and air quality. A third aim is to determine the role of new P inputs in forests by deposition and weathering vs recycled P due to litterfall  and mineralization on forest growth and carbon sequestration, by assessing P balances at regional scale (e.g. The Netherlands and Europe).